Angle Grinder

ABSTRACT

The present invention relates to an angle grinder having a front transmission housing for enclosing a transmission arrangement which has a closing surface that faces away from a free end of the tool spindle, and wherein the maximum distance between the closing surface and an end face of the free end of a tool spindle defines a height of the transmission housing, and wherein the height has a predefined ratio to a diameter of a disc-shaped tool, of about 1 to about 5.

The present invention relates to an angle grinder. In the presentapplication, the term angle grinder is also intended to include typicalparting-off grinders.

A multiplicity of angle grinders of the type mentioned, above, havebecome known from the prior art. In those cases, various possibilitiesfor realizing an angle transmission arrangement have been proposed,including the use of belt drives (for example, according to DE 43 42 986C1). Also known from the prior art are angle transmission arrangementshaving a pinion gear on the motor shaft and having a bevel gear or crownwheel that is fastened to the tool spindle (e.g. DE 100 65 658 A1 orU.S. Pat. No. 6,386,961 B1). Finally, flexible drive shafts have alsobeen proposed in the prior art (cf., for example, EP 0 579 949 A1).

The applicant's German patent applications DE 10 2008 059 247 A1 and DE10 2009 053 614 A1 likewise deal with the actual design of an anglegrinder, which, in particular, has a compact, flat-structuredtransmission housing, to make it easier for the angle grinder to accessconfined working spaces such as, for example, acute-angled corners orthe like.

For this purpose, my application DE 10 2008 059 247 A1 discloses ahat-shaped crown-wheel angle transmission arrangement, and wherein therecess of the crown wheel is oriented so as to face towards the tool, ortowards the free end of the tool spindle.

DE 10 2008 059 247 A1 proposes that the tool spindle be provided as onepiece and have at least one bearing seat portion for a rolling bearing,a portion of the angle transmission arrangement that is realized as acrown wheel, a support portion for the abrasive tool or for a supportflange for the abrasive tool, and a threaded portion for a clampingmeans for fixing the abrasive tool to the tool spindle. The purpose ofthe one-piece arrangement is to achieve a particularly compact design.

The present invention is therefore based, at least in part, on theobject of providing an alternative solution for an angle grinder, of thetype described above, and which likewise is of a compact,flat-structured design, at least in the region of the transmissionhousing of the angle transmission arrangement.

This object is achieved, according to the invention, by an angle grinderhaving the features of the claims as provided hereinafter.

Accordingly, there is proposed an angle grinder having a motor fordriving a tool spindle, and wherein the tool spindle is arranged, bymeans of an angle transmission arrangement, at an angle in relation to adriving shaft of the motor, and wherein the angle transmissionarrangement is accommodated or enclosed in an associated transmissionhousing, from which there is able to extend a free end of the toolspindle, and to which a disc-shaped tool, which can rotate about thecentral longitudinal axis of the tool spindle, can be fastened by meansof a tool flange. According to the teachings of the present invention,the transmission housing is realized or formed in such a manner that atleast the front transmission housing of the angle transmissionarrangement has a closing surface that faces away from the free end ofthe tool spindle, and wherein the maximum distance between this closingsurface and an end face of the free end of the tool spindle defines aheight of the transmission housing, and wherein the height has apredefined ratio to the diameter of the disc-shaped tool, of maximally 1to 2, and in particular of 2 to 5.

The free end of the tool spindle is thus defined as the region thatprojects out of the transmission housing and to which the tool can beattached.

The tool flange in the present application constitutes a support portionfor the disc-shaped tool, and which can be brought to bear against thelatter, at least partially, in order to assume a defined positionrelative to the tool spindle. For the purpose of fastening to the toolspindle, a clamping means such as, for example, a clamping nut, may beused to clamp the tool against the tool flange. The tool flange in thiscase may be realized as a separate element that can be fastened to thetool spindle, or it may be realized or formed so as to constitute asingle piece with the tool spindle.

Usually, during use of an angle grinder, such as the angle grinderaccording to the teachings of the present invention, the region of thedisc-shaped tool that is used to perform work is that which extendsforwards from the tool spindle, i.e. away from the motor. Accordingly,the transmission housing dimensions in precisely this front region arealso particularly relevant to the access capability of the angle grinderin the case of a confined working space. As should be understood, thefront region of the transmission housing is the region that, relative tothe longitudinal axis of the driving shaft of the motor driven, extendsaxially from the tool spindle to the front end of the transmissionhousing, i.e. the end facing away from the motor.

By definition, therefore, the closing surface that faces away from thefree end of the tool spindle constitutes the highest portion of thefront transmission housing in this region, i.e. the most axially distantfrom an end face of the free end of the tool spindle, and consequently,together with the end face, delimits the relevant height of the fronttransmission housing.

The closing surface that faces away from the free end of the toolspindle is constituted or defined by an outer surface of thetransmission housing in the region of the tool spindle. The closingsurface of the housing and the end face of the tool spindle may berealized or formed such that they are parallel to each other, orrealized such that they are inclined relative to each other. In thisarrangement, the maximum distance between them defines, at least, theheight of the angle grinder in the region of the tool spindle, and theheight having a predefined ratio of at least 2 to 5 relative to thediameter of the disc-shaped tool. This ratio of the height to thediameter of the tool, for example and which is realized as an abrasivedisc, makes it possible, in turn, to ensure that the angle grinder isbetter able to access confined, or acute-angled, corners.

Furthermore, it may be provided in one form of the invention that theclosing surface of the tool flange that faces toward the tool spans anotional plane that intersects the motor, at least partially.

The closing surface of the tool flange that faces towards the free endof the tool spindle denotes the side of the tool flange that is closestin the free end of the tool spindle and that projects out of thehousing. As described above, this normally coincides with the top sideof a disc-shaped tool which is in bearing contact and which furtherfaces towards the transmission housing, and which additionally defines anotional plane that is offset relative to the motor housing, and themotor, such that it intersects the motor, at least partially.

The transmission housing thus has a smaller axial extent (in respect ofthe tool spindle axis), than the motor housing and the motor locatedtherein, at least in the region of the tool flange.

Furthermore, it may be provided that a tangent that, starting from acircumferential edge of the disc-shaped tool, can be placed against thetransmission housing, and which further encloses, together with thenotional plane, an angle of maximally 40°, and in particular maximally35°, and preferably less than 34°. Consequently, a tangent is defined asthat, line starting from a circumferential edge of a disc-shaped tool,and which is placed against the transmission housing. The slope of thetangent, as provided, thus depends on two factors, namely, on the onehand, the diameter of the abrasive tool used and, on the other hand, theactual design of the transmission housing, and in particular bevels,which are possibly applied to the housing, and which have a slope thatis favourable relative to the tangent. This likewise notional tangent,with the notional plane defined above, encloses an angle of maximally40°. Clearly, the lesser the angle, the more the access capability ofthe angle grinder, and therefore its handling characteristics, are alsoimproved.

It is possible, in principle, to project the circumferential edge of thedisc-shaped tool into the notional plane, in order to achieve a uniformspecification of the angle described, above. In this way, thetangent—irrespective of the actual design of the tool, whether as adish-shaped disc or as a flat disc—always has the same slope for discshaving the same diameter. Alternatively, however, it is also possible totake as a basis the actual circumferential edge, since the latterdetermines the actual access capability of the angle grinder, inpractice. In this case, the actual design of the tool, whether as adish-shaped disc or as a flat disc, also determines the slope of theresulting notional tangent.

It may additionally be provided, advantageously, that the radius of thedisc-shaped tool is smaller than the radial extent of the transmissionhousing from the central longitudinal axis of the tool spindle.Accordingly, the radial extent of the transmission housing runsparallelwise in relation to the tool plane. According to the teachingsof the present invention, the transmission housing has a comparativelysmall measurement in the axial direction (in respect of the centrallongitudinal axis of the tool spindle), out from the centrallongitudinal axis of the tool, but in the radial direction has a greatermeasurement than the radius of the disc-shaped tool. in combination withthe offset, according to the teachings of the present invention, thetransmission housing, whose notional plane is able to intersect themotor, at least partially, the transmission housing can be provided in aform that is axially shorter than the motor housing. In thisarrangement, the access capability of the angle grinder is greatlyimproved. Owing to this radially comparatively elongate realization ofthe transmission housing, the abrasive disk can be attached close to theclosing surface of the transmission housing which faces towards the freeend of the tool spindle, and irrespective of the dimension of the motorhousing. As will be recognized, the part of the tool spindle projectingout of the transmission housing can be kept comparatively short.

Furthermore, in one possible form of the invention, the angletransmission arrangement may have a crown wheel, and wherein the crownwheel is substantially hat-shaped, and further has a full-perimeterflange and a receiving portion that forms the hat shape, wherein atoothing of the crown wheel is provided on the flange, and wherein thereceiving portion is suitable for receiving at least one part of abearing means that supports the tool spindle relative to thetransmission housing.

The receiving portion of the crown wheel is thus open in one direction,and wherein the opening of the receiving portion is thus delimited inthe other direction by a projection which is formed towards the otherside of the crown wheel. This projection may be dome-shaped and have,for example, a cylindrical or conical basic shape, as viewed from theoutside.

The bearing means as mentioned, above, may comprise, in particular, tworolling bearings that serve to support the tool spindle in a rotatablemanner inside the transmission housing. In one embodiment of theinvention, the receiving portion is able to receive, not just one but,if necessary, also a plurality of bearings and which constitute thebearing means. In this way, it is possible to save yet more structuralspace in the axial direction, as compared with the prior art teachings.

The toothing of the crown wheel (as mentioned, above) serves to engagewith a pinion gear that is driven by the motor shaft. The torque is thustransmitted from the motor shaft to the tool spindle via the toothing ofthe crown wheel. In this arrangement, the crown wheel can be connectedto the tool spindle in a rotationally fixed manner, and wherein the toolspindle is rotatably mounted inside the transmission housing, forexample by means of two rolling bearings which constitute a bearingmeans.

According to one embodiment of the present invention, the toothing ofthe crown wheel may be arranged on a side of the crown wheel that facestowards the free end of the tool spindle. In such an arrangement of thetoothing of the crown wheel, the opening of the receiving portion of thecrown wheel is preferably oriented away from the free end of the toolspindle, in order to provide a particularly space-saving realization ofthe crown wheel in the axial direction.

Alternatively, the toothing of the crown wheel may also be arranged on aside of the crown wheel that faces away from the free end of the toolspindle. In the case of this design variant, the opening of thereceiving portion of the crown wheel may possibly be oriented towardsthe free end of the tool spindle.

As a further conceivable alternative, however, it is also possible forthe angle transmission arrangement to have a crown wheel that issubstantially disc-shaped, and wherein a toothing, which is arranged onone side of the crown wheel, is provided at the outer edge of the crownwheel. In this arrangement, at least one part of a bearing means thatsupports the tool spindle relative to the transmission housing, andpreferably all parts of the bearing means, is or are arranged, relativeto the crown wheel, on the same side as the toothing.

Further advantages and particular features of the present invention willbe understood by the claims and by the following description of thefigures, and the drawings which are provided, herewith.

The present invention is described in greater detail in the followingparagraphs with reference to the appended drawings, and wherein thelatter represent, by way of example, preferred embodiments of theinvention in which the individual features of the invention have beencombined with each other. Clearly, however, persons skilled in the artwill also be able to consider these separately from each other and/orcombine them into appropriate combinations.

In the drawings:

FIG. 1 shows an angle grinder according to the teachings of the presentinvention, and which is represented in a longitudinal sectional view;

FIGS. 2 a to 2 c show differing variants of a crown wheel which forms afeature of the angle grinder according to the present invention, andwhich is represented schematically in a longitudinal sectional view.

FIG. 1 shows a power tool according to the invention, and which isillustrated in the form of an angle grinder 10 according to a firstembodiment. The latter differs from the embodiments of FIGS. 2 a to 2 csolely in the actual design of an angle transmission arrangement 14 ofthe angle grinder 10. For features that are the same, therefore, thevariants shown in FIGS. 2 a to 2 c have the same references, but withthe prefixed numerals “1”, “2” or “3”, respectively, according to theembodiment.

The angle grinder, as seen in FIG. 1 has been illustrated as it would beseen along a central longitudinal axis L₁, and which comprises a motor12. The motor further comprises a stator 12 a, which encompasses a rotor12 b that, with a driving shaft 12 c of the motor 12, rotates about thelongitudinal axis L₁ thereof. Additionally an angle transmissionarrangement 14, is provided for transmitting the torque from the drivingshaft 12 c of the motor 12 to a tool spindle 18 and which is arranged atan angle relative thereto. The angle transmission arrangement 14 isaccommodated in a transmission housing 16 and comprises, in addition tothe tool spindle 18, a tool flange 20, which, together with a clampingnut 34, serves to fasten a disc-shaped tool 22 to the tool spindle 18, abearing means 28, for supporting the tool spindle 18 inside thetransmission housing 16, and a crown wheel 24, which is provided to takeoff the input torque from the driving shaft 12 c. The tool spindle 18,together with a tool 22 fastened thereto, is able to rotate about itscentral longitudinal axis L₂.

As shown clearly by FIG. 1, the tool flange 20 is arranged with anupward offset relative to the (in FIG. 1) lower edge of the motor stator12 a as shown in FIG. 1, such that its closing surface 20 a that facestowards the tool spans a notional plane E that intersects the motor 12in the region of its stator 12 a.

On the basis of this specific design of the angle transmissionarrangement 14, a particularly flat and space-saving design of the anglegrinder 10 is provided in the region of its disc-shaped tool 22, thusenabling the angle grinder to be used even in regions in which theavailable working space is comparatively small (e.g. in the case ofacute-angled corners). As can also be seen from FIG. 1, and in theregion of the tool spindle 18, the transmission housing 16 comprises aclosing surface 16 a that faces away from the free end of the toolspindle 18, as well as a housing cover 16 b, which is arrangedparallelwise in relation to said surface.

Usually, during the use of an angle grinder, such as the angle grinder10 and as seen in FIG. 1, the region of the disc-shaped tool 22 which isused is that portion which extends forwards away from the tool spindle18, i.e. away from the motor 12. Accordingly, the transmission housingdimensions in precisely this front region are also particularly relevantto the access capability of the angle grinder in the case of a confinedworking space. In the following specification, the front region of thetransmission housing is understood to be that region that, in respect ofthe longitudinal axis L₁, extends axially from the tool spindle to thefront end of the transmission housing (that faces away from the motor12).

By definition, therefore, the closing surface 16 a that faces away fromthe free end of the tool spindle constitutes the highest or mostelevated portion of the front transmission housing 16 in this region,i.e. the most axially distant from an end face 18 a of the free end ofthe tool spindle 18, and consequently, together with the end face 18 a,delimits or defines a height dimension H for the front transmissionhousing 16.

A further quantity that, apart from this height H, is relevant to theaccess capability of the angle grinder 10 in, for example, room cornersor the like, is the slope of a tangent T, which is denoted by the anglea (FIG. 1). In this case, the tangent T runs or extends from acircumferential edge of the tool 22, along the transmission housing 16,and, together with the notional plane E, encloses or defines the angleα. The smaller the height or elevation dimension H, and the flatter theslope of the tangent T, the better is the access capability of the anglegrinder 10 in restricted working spaces.

As shown in FIG. 1, it is possible, in principle, to project thecircumferential edge of the disc-shaped tool 22 into the notional planeE (projection point P), in order to achieve a uniform specification ofthe angle a described above. In this way, the tangent T—irrespective ofthe actual design of the tool 22, whether as a dish-shaped disc, as inFIG. 1, or as a flat disc—always has the same slope for discs having thesame diameter.

Alternatively, however, it is also possible to take as a basis orreference the actual circumferential edge of the disc 22, since thelatter determines the actual access capability of the angle grinder 10in practice. In this case, and in addition to the diameter D and theheight H, the actual design of the tool 22, whether as a dish-shapeddisc or as a fiat disc, also determines how well the angle grinder 10reaches into working spaces that are difficult to access.

The other dimensions of the transmission housing 16, from the region ofthe tool spindle 18 towards the motor 12, are therefore only ofrelevance to the access capability insofar as these may not have anyprojections that project beyond the tangent T, or insofar as it must bepossible for the disc-shaped tool 22 to bear against the tool flange 20in an unimpeded manner.

Accordingly, as can be seen from FIG. 1, the radial extent of thetransmission housing 16, from the tool spindle 18, or from its centrallongitudinal axis L₂, in the direction towards the motor 12, along thelongitudinal axis L₁ of the driving shaft 12 c of the motor 12, is alsodimensioned so as to be greater than the radius D/2 of the disc-shapedtool 22. In this way, the tool 22 can easily bear against the toolflange 20 in an unimpeded manner, and a particularly flat structure ofthe transmission housing 16 is provided, irrespective of the design ofthe motor housing (not represented).

A further special feature of the present invention is to be seen in thedesign of the angle transmission arrangement 14, and in particular thecrown wheel 24. According to the teachings of the present invention,differing structural forms are proposed for the crown wheel, and whichenable the angle transmission arrangement to have a structure that is asspace-saving as possible.

In the case of the embodiment shown in FIG. 1, the crown wheel 24 isprovided in the form of a disc. This is also the case of the variantshown in FIG. 2 a, and wherein, provided at the outer edge 26, 126 ofthe crown wheel 24, 124, there is a toothing 126 a (cf. FIG. 2 a), whichis arranged on the same side of the crown wheel as the bearings whichform a bearing means 28, 128. The toothing serves, in a known manner, totransmit the driving torque of the driving shaft 12 c of the motor 12from a drive pinion 30 to the crown wheel 24, and thereby to the toolspindle 18. In this case, and as shown, the crown wheel 24 may berealized as a separate element that is connected to the tool spindle 18in a rotationally fixed manner, or alternatively it may be provided asto constitute a single piece with the tool spindle.

Since, according to the teachings of the present invention, the toothingis arranged on the same side of the crown wheel as the bearings of thebearing means, the structural space required for the bearing means inthe axial direction (with regard to the central longitudinal axis L₂ ofthe tool spindle 18) is also used at the same time for the arrangementof the toothing 126 a of the crown wheel, and for the engagement of thetoothing in the drive pinion 30.

In the case of an alternative configuration of the crown wheel accordingto FIGS. 2 b and 2 c, the crown wheel is not disc-shaped, but hat-shapedand, in addition to having an outer flange 226, 326, on which thetoothing 226 a or 326 a, respectively, is realized, has a receivingportion 232, 332 that forms the hat shape.

The receiving portion 232, 332 of the hat-shaped crown wheel 224, 324 isdelimited by a projection 232 a, 332 a, which is dome-shaped and has,for example, a cylindrical or conical basic shape, as viewed from theoutside, although this is not absolutely necessary. The receivingportion serves to receive at least one part of the bearing means 228,328, i.e., for example, as shown in FIG. 2 b, one of the rollingbearings 228 a of the bearing means 228, or even, as shown in FIG. 2 c,both rolling bearings of the bearing means 328. The toothing 226 a or326 a, respectively, is in each case realized on a side of the crownwheel 224, 324 that faces away from the opening of the receiving portion232, 332. Since the toothing 226 a, 326 a is provided on the side of thecrown wheel on which the projection 232 a, 332 a extends, the axialstructural space required for this in any case (in respect of thelongitudinal axis L₂ of the tool spindle 18) is again used at the sametime for the pinion shaft 230, 330, thus reducing the axial structuralheight.

Regardless of the design of the crown wheel, which is selected, therolling bearings of the bearing means 28 can be secured in theirposition inside the housing 16, in the usual manner, by projections orshoulders on the transmission housing 16 and by the provision of acirclip or the like.

1. An angle grinder comprising: a motor for driving a tool spindle, andwherein the tool spindle is arranged, by means of an angle transmissionarrangement, at an angle in relation to a driving shaft of the motor,and wherein the angle transmission arrangement is enclosed, at least inpart, in an associated transmission housing, and from which extends afree end of the tool spindle, to which a disc-shaped tool, which canrotate about a central longitudinal axis of the tool spindle, can befastened by means of a tool flange, and wherein at least a front of thetransmission housing of the angle transmission arrangement has a closingsurface that faces away from the free end of the tool spindle, andwherein the maximum distance between the closing surface and an end faceof the free end of the tool spindle defines a height of the transmissionhousing, and wherein the height has a predefined ratio to the diameterof the disc-shaped tool, of maximally 1 to 2, and preferably of 2 to 5.2. An angle grinder as claimed in claim 1, and wherein the closingsurface of the tool flange that faces in a direction towards the toolspans a notional plane that intersects the motor, at least partially. 3.An angle grinder according to claim 2, and wherein a tangent that isdefined as a line extending from a circumferential edge of thedisc-shaped tool and which is further oriented against the transmissionhousing, and encloses, together with the notional plane, an angle of amaximally angular value of less than about 40°, and preferably less than34°.
 4. An angle grinder as claimed in claim 3, and wherein a radius ofthe disc-shaped tool is smaller than the a radial dimension of thetransmission housing when measured from the central longitudinal axis ofthe tool spindle.
 5. Angle An angle grinder as claimed in claim 4, andwherein the angle transmission arrangement has a crown wheel, andwherein the crown wheel is substantially hat-shaped, and further has afull-perimeter flange and a receiving portion that forms the hat shape,and wherein a toothing of the crown wheel is provided on the flange, andwherein the receiving portion is suitable for receiving at least onepart of a bearing means that rotatably supports the tool spindlerelative to the transmission housing.
 6. An angle grinder as claimed inclaim 5, and wherein the toothing of the crown wheel is arranged on aside of the crown wheel that faces towards the free end of the toolspindle.
 7. An angle grinder as claimed in claim 6, and wherein theopening of the receiving portion of the crown wheel is oriented awayfrom the free end of the tool spindle.
 8. An angle grinder as claimed inclaim 5, and wherein the toothing of the crown wheel is arranged on aside of the crown wheel that faces away from the free end of the toolspindle.
 9. An angle grinder as claimed in claim 4, and wherein theangle transmission arrangement has a crown wheel which is substantiallydisc-shaped, and wherein a toothing, which is arranged on one side ofthe crown wheel, is provided at the outer edge of the crown wheel, andwherein at least one part of a bearing means that rotatably supports thetool spindle relative to the transmission housing, and wherein all partsof the bearing means are arranged on the same side of the crown wheel.